Fix thread-safety when fetching user secret in Google Colab (#1953)
* Fix thread-safety when fetching user secret
* unused var
* request secret only once
* Update src/huggingface_hub/utils/_token.py
Co-authored-by: Omar Sanseviero <osanseviero@gmail.com>
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Co-authored-by: Omar Sanseviero <osanseviero@gmail.com>